Centrifugal fan.



W. E. ALLINGTON.

OENTEIFUGAL FAN. ABPLIGATION FILED SEPT. 7, 1909.

Patented Apr. 14!, 1914.

I LrAM E.:ALLINGTON, or snemaw, MICHIGAN.

CENTRIFUGAL FAN.

To all 1071072 it may concern:

Be it known that I, IVILLIAM E. ALLING- run, a citizen of the United States, residing at Saginaw, in the county of Saginaw and ance space on thefront or inletside of the wheel, as illustrated in my prior Patent No. 865,962.

My present invention contemplates the provision, in a fan of the character de scribed, of a guard projecting inwardly from the front wall of the casing nearly to the wheel intermediate the inlet and the line of travel of the blade tips, and further the provision of a guard extension in the same lateral area of the casing, projecting from the guard to the peripheral wall of the fan, preferably in substantial alinement with the inner edge of the tangential out-let.

In the drawings, wherein I have illustratcd an embodiment of my invention, Figure 1 is a side elevation, with parts broken away, of a fan embodying my invention; and Fig. 2 is acentral section .therethrough.

The fan herein illustrated is of a type shown in my Patent No. 865,962 and comprises a scroll-shaped fan-casing, 5, having a front wall, 6, provided with an axial inlet, 7, and'a rear wall, indicatedat S.

9 indicates the wheel-supporting shaft extending through the rearwall and carrying a fan-wheel, 10, having a plurality of blades,

.11, each angularly bent to a forward pitch at its tip and its front edge toward the front side of the casing, sloping back from a point, 12, both toward the tip and the base of the blade. The fan-wheel is arranged near the rear wall ofv the casing to leave between its front side and the front wall, 6, of the casing a relatively large side clearance, 13, such clearance space being preferably about one-third of the lateral dimension or depth of the casing. Within said side clearance space, I providea guard wall, 14, preferably circular in configuration,\ projecting inwardly from the front wall 6 iii-parallelism to the axis of the fan-wheel and concentric therewith, said wall being preferably placed Specification of Letters Patent. Application filed September 7, 1909.

flow within its own casing,

Patented Apr, 14, Mill t. Serial No. 516,318.

intermediate the inlet 7 and the projection of the circle of travel of the tips of the blades 11 in the neighborhood of the angle of the blades and in arrangement to approach atits inner edges rather closely to said blades, though leaving a small clearance. From the guard 14 a guard extension, 15, projects in the same lateral area as the guard to the scroll-wall of the fan-casing. preferably in horizontal aliuement with the inner wall of the tangential outlet 5, as best shown in Fig. 1. This entire guard struc tine-annulus and extensionmay convenient-ly be made of a single piece of metal, curled and riveted into the form of a circular band with a tangential extension. It will be obvious to those skilled in the art, however, that the details involved in the illustrated embodiment of the idea might be varied without departure'from the spirit of the invention.

In operation, the circular guard 14 acts to transform the otherwise open clearance space 13'into two separated areas, the one a large circular intake-chamber surrounding the fan inlet, and the other a scroll-shaped lateral extension of the air-flow space peripherally beyond the fan-wheel, so that air may not easily back from the outer air of the clearance space into the inlet; and further, the tangential guard 15 interrupts the continuity of the side clearance space so as to prevent the reversal of current flow therein and guard against the idle rotation of the air in said space, wholly within the casing is manifest. By the arrangement described,

I am able to retain the advantages of a wide casing with a large clearance space laterally beyond the blades toward the inlet side of the fan and yet to .prevent the fan from being afiected by short circuiting of its air and toward its inlet, such as a relatively high resistance is apt otherwise to engender. In such construction, further, it will be noted that the arrangement of the guard at the point of maximumwidth of the fan,-or at that point from which the fan blade'slopes backwardly away from the clearance space, radially outwardly and inwardly,,-attains, by cooperation between the fan casing, the guard, and

the particular fan construction, two well separated areas, each having one side bounded by the front plate of the fan casing and the other side bounded by sloping edgesof the fan blades, the two areas having such sloping edges difl'erently inclined, as will be apparent from the drawings. I have found from practical ex-' perience that this construction attains excellent results, presumably because it provides an unrestricted intake capacity co-extensive with one of the tapering zones of the blades of the fan, and a surrounding scroll shaped area within which the other zone of the blades lies so that the tendency of the air to back up or short circuit is practically avoided even where long pipe leads present great resistance to the flow of air.

What I claim is:

1. A centrifugal .fan providing a relatively deep casing, having an axial side inlet, and a peripheral outlet; a relatively narrow fan wheel in the rear portion of said casing opposite the axial inlet to leave a relatively large clearance space on the inlet side of the casing, said fan wheel providing blades each having its front edge sloping from a point of maximum width toward the heel of the blade in a direction receding from the inlet, and a circular guard within said clearance space, said guard being of a greater diameter than the inlet, and arranged to oppose and. extend substantially to said point of maximum width of the wheel blade to divide said clearance space into a relatively large intake chamber into which the inlet opens, and an area conforming to the peripheral wall of the casing, and communicating with the intake chamber only through the field of operation of the fan 'wheel. 7 I

2. A centrifugal fan providing a relatively deep casing, having an axial side in- Y let, and a peripheral outlet; a relatively narrow fan wheel in the rear ortion of said casing opposite the axial n et to leave a relatively lar'ge'clearance space on the inlet side of the casing, said fan wheel providing blades each having its front edge sloping from a point of maximum width toward the heel of the blade in a direction receding from the inlet, and a circular guard within the clearance space, said guard being of a greater diameter than the inlet, and arranged to oppose "and extend substantially to said point of maximum width of the wheel blade to divide said clearance space into a relatively large intake chamber into which the inlet opens, and an area conforming to the peripheral wall of the casing, and

communicating with the intake chamber only through the field of operation of the fan wheel, said circular guard wall having a tangential extension connecting the circular wall with the peripheral wall of the casing adjacent the outlet.

3. A centrifugal fan comprising a fan casing having an inlet eye and a tangential outlet, a guard concentric with said inlet eye and provided with an integral extension paralleling the outlet, said guard and extension extending inwardly at right angles.

from the inlet side of the fan casing a distance approximating a third of the width of the casing, and the guard lying in a circle radially spaced from the edge of the inlet eye by a distance approximating the distance of its extension-inward from the front of the casing, and afan having a plurality of blades, each having a front edge portion adjacent the free inner edge of said guard,

the edge sloping from such point of coaction withthe guard respectively toward the lteel and toward the tip of the blade as de.

scribed.

Intestimony whereof I hereunto set my hand in the presence of two witnesses.

WILLIAM E. ALLINGTON. 

